ISO containers, also called shipping containers or intermodal containers, are used for intermodal transport of freight. They are manufactured according to specifications from the International Standards Organization (ISO) and are suitable for multiple transportation methods such as truck, rail, and ship. ISO containers are manufactured in many sizes. Standard containers are typically 8 ft. wide and 8.5 ft. tall. The most common lengths are 20 and 40 ft. Other lengths include 24, 28, 44, 45, 46, 53 and 56 ft. There are several basic types of ISO containers. The sizes of the ISO containers are selected so that they are within load profiles that exist for railway and road transport systems.
After usage the container has to be cleaned. This is often done in a certain place, for example, a harbor or a logistic centre. A large number of containers are handled in the same place. For facilitating the transportation of the containers, for example, between the transport means, such as ship, trains or lorries and the cleaning station, specially designed trucks have been developed for picking up and moving ISO containers.
Traditionally, the cleaning of the containers is made by using a solvent in combination with high pressure wash. This means that the waste water produced during the cleaning is contaminated with the solvent as well as the dirt removed from the container. A disadvantage with this cleaning method is that it produces a large amount of waste water which has to be collected and purified in order to avoid negative environmental influence. The cost for building a plant for collecting and purifying the waste water is extensive. A further disadvantage with this cleaning method is that it takes a long time for the container to dry after the cleaning has been finished.
The cleaning of the ISO containers is usually carried out by humans operating a high-pressure wash by hand. However, from U.S. Pat. No. 5,624,745 it is known to use a robot for cleaning large storage tanks having a small access opening, such as those commonly used in petrochemical plants or in oil refineries. The robot is provided with an articulated nozzle for supplying a cleaning medium including water and a diluent, such as diesel fuel. The robot is enclosed in a chamber having an opening sized and adapted to attach to the access opening of the container. An actuating unit is arranged to move the robot between the chamber and the interior of the container.
A well-known cleaning method from other areas is dry ice blasting, also known as CO2 ice blasting. Dry ice blasting uses compressed air to accelerate frozen carbon dioxide (CO2) “dry ice” pellets to a high velocity. The dry ice pellets are accelerated at supersonic speeds, and creates mini-explosions on the surface to lift the undesirable item off the underlying substrate. The dry ice blasting technique has many advantages, for example, it is environmentally-friendly and contains no secondary contaminants such as solvents or grit media, it is clean and approved for use in the food industry, and can be used without damaging active electrical or mechanical parts or creating fire hazards.
WO9639277 discloses a method for removing explosives deposits in effluent pipes or from ammunitions casings. The explosive is removed from the wall of the pipe with the aid of dry ice blasting. A robot carrying a nozzle is used for providing the dry ice to the walls of the pipe.